At a low part-load and idling it is difficult to achieve a good fuel economy and acceptable emission rates of a vehicle machinery. When said machinery comprises a gas turbine, the work for driving the compressor and auxiliary apparatuses is very heavy during said operation conditions.
For normal driving there should be a certain power available, and in order to counteract the above mentioned disadvantages at part load and idle running, it is proposed, according to the present invention, that the turbine, including its combustor, is so formed that at a low r.p.m. it is not able to drive the main rotor alone, i.e. the rotor comprising the compressor, as well as the auxiliary apparatuses. An additional motor, which may be of different types, is therefore arranged to supply the necessary additional power, which may be carried out with a satisfactory fuel economy and exhaust gas emissions.